The Internet enables a user of a client computer system to identify and communicate with millions of other computer systems located around the world. A client computer system can identify each of these other computer systems using a unique numeric identifier for that computer called an “IP address.” When a communication is sent from a client computer system to a destination computer system, the client computer system typically specifies the IP address of the destination computer system in order to facilitate the routing of the communication to the destination computer system. For example, when a request for a World Wide Web page (“Web page”) is sent from a client computer system to a Web server computer system (“Web server”) from which that Web page can be obtained, the client computer system typically includes the IP address of the Web server.
In order to make the identification of destination computer systems more mnemonic, a Domain Name System (DNS) has been developed that translates a unique alphanumeric name for a destination computer system into the IP address for that computer. The alphanumeric name is called a “domain name.” For example, the domain name for a hypothetical computer system operated by IBM Corporation may be “comp23.IBM.com”. Using domain names, a user attempting to communicate with this computer system could specify a destination of “comp23IBM.com” rather than the particular IP address of the computer system (e.g., 198.81.209.25).
A user can also request a particular resource (e.g., a Web page or a file) that is available from a server computer by specifying a unique Universal Resource Indicator (“URI”), such as a Uniform Resource Locator (“URL”), for that resource. A URL includes a protocol to be used in accessing the resource (e.g., “http:” for the HyperText Transfer Protocol (“HTTP”)), the domain name or IP address of the server that provides the resource (e.g., “comp23IBM.com”), and optionally a path to the resource (e.g., “/help/HelpPage.html”)—thus “http://comp23IBM.com/help/HelpPage.html” is one example of a URL. In response to a user specifying such a URL, the comp23IBM.com server would typically return a copy of the “HelpPage.html” file to the user.
In addition to making the identification of destination computer systems more mnemonic, domain names introduce a useful layer of indirection between the name used to identify a destination computer system and the IP address of that computer system. Using this layer of indirection, the operator of a particular computer system can initially associate a particular domain name with a first computer system by specifying that the domain name corresponds to the IP address of the first computer system. At a later time (e.g., if the first computer system breaks or must be replaced), its operator can “transfer” the domain name to a second computer system by then specifying that the domain name corresponds to the IP address of the second computer system.
The domain names in DNS are structured in a hierarchical, distributed database that facilitates grouping related domain names and computers and ensuring the uniqueness of different domain names. In particular, as mentioned above, a particular domain name such as “IBM.com” may identify a specific host computer. However, the hierarchical nature of DNS also allows a domain name such as “IBM.com” to represent a domain including multiple other domain names each identifying computers (also referred to as “hosts”), either in addition to or instead of identifying a specific computer.
FIG. 20 illustrates a hypothetical portion of the DNS database 2000 in which the node representing the IBM.com domain name 2010 is the root node in an IBM.com domain 2050 that includes 7 other nodes each representing other domain names. Each of these domain names in the IBM.com domain can be, but do not have to be, under the control of a single entity (e.g., IBM Corporation). FIG. 20 also includes a WebHostingCompany.com domain 12055 that includes a single domain name.
As illustrated, the DNS database can be represented with a hierarchical tree structure, and the full domain name for a given node in the tree can be determined by concatenating the name of each node along the path from the given node to the root node 2001, with the names separated by periods. Thus, the 8 nodes in the IBM.com domain represent the domain names IBM.com 2010, foo.IBM.com 2012, foo.foo.IBM.com 2018, bar.foo.IBM.com 2020, bar.IBM.com 2014, comp23IBM.com 2016, abc.comp23IBM.com 2022, and cde.comp23IBM.com 2024. Other “.com” domain names outside the IBM.com domain are also illustrated in FIG. 20, including the second-level domain names BCD-Corp.com 2032, WebHostingCompany.com 2034, 1-800-555-1212.com 2042 and 123456.com 2044, and the lower-level domain names 123.123456.com 2046 and 456.123456.com 2048. In addition to the “.com” top-level domain (“TLD”), other TLDs are also illustrated including the “.cc” geographical TLD and the “.gov”, “.edu” and “.mil” organizational TLDs. Illustrated domain names under these other TLDs include Stanford.edu 2036, Berkeley.edu 2038, and RegistrarCompany.cc 2040.
New domain names can be defined (or “registered”) by various domain name registrars. In particular, a company that serves as a registrar for a TLD can assist customers in registering new domain names for that TLD and can perform the necessary actions so that the technical DNS information for those domain names is stored in a manner accessible to name servers for that TLD. Registrars often maintain a second-level domain name within the TLD (e.g., a hypothetical Registrar Company that acts as a registrar for the “.cc” TLD could maintain the RegistrarCompany.cc domain name 2040), and provide an interactive Website at their domain name from which customers can register new domain names. A registrar will typically charge a customer a fee for registering a new domain name.
For the “.com”, “.net” and “.org” TLDs, a large number of registrars currently exist, and a single shared registry (“the Registry”) under the control of a third-party administrator stores information identifying the authoritative name servers for the second-level domain names in those TLDs. Other TLDs may have only a single registrar, and if so that registrar could maintain a registry for all the second-level domains in that TLD by merely storing the appropriate DNS information for each domain name that the registrar registers. In other situations, multiple registrars may exist for a TLD, but one of the registrars may serve as a primary registrar that maintains a registry for each of the second-level domains in that TLD—if so, the secondary or affiliate registrars for that TLD supplies the appropriate DNS information for the domain names that they register to the primary registrar. Thus, the manner in which the DNS information for a TLD is obtained and stored is affected by the registrars for that TLD.
While the DNS system provides many benefits, various problems exist. For example, there are currently a limited number of TLDs, and many available domain names in the most popular TLDs (e.g., “.com”) have already been taken. Thus, users will often have difficulty identifying available or non-registered domain names, i.e., domains that therefore do not exist in the authoritative registry for the TLD, that are “non-existent domains” also termed NXDomains or NXDs. A user may, instead, often attempt to register domain names that are already registered. In such a situation, the user will be prevented from registering the domain name, but may receive little or no assistance in determining other domain names that are available. For example, the user will typically have to identify other domain names to consider without assistance. If the user is able to identify any other domain names, it is then difficult for the user to determine whether those other domain names are available. Typically, the user will need to attempt to register each of those other domain names one-at-a-time to determine if they are available. This is a time-consuming and inefficient process.